The present invention relates to bicycle accessories and, more particularly, to guards for protecting the rear derailleurs of multiple-speed bicycles.
The derailleur speed change system provides a lightweight, easily-operable mechanism for changing speeds on a bicycle. Typically, the derailleur system includes a sprocket with five gears of varying sizes mounted on the rear axle of the bicycle, and a rear derailleur having a set of idler wheels which are sidewardly displaceable to cause the chain extending between the front and rear sprockets to disengage one gear and engage another.
The rear derailleur is mounted on the rear wheel axle and projects sidewardly from the bicycle frame. Consequently, the rear derailleur is susceptible to damage from blows received when the bicycle falls on the side of the derailleur so that the derailleur lands upon the ground or, as frequently happens in a racing situation, the rear derailleur contacts part of an adjacent bicycle. Consequently, there is a need for a guard to prevent damage to the relatively delicate rear derailleur of a bicycle.
Some derailleur guards are already in use. For example, Swenson U.S. Pat. No. 3,184,993 discloses a derailleur guard which comprises a plate shaped to partially enclose a rear derailleur. The derailleur plate is mounted on the rear axle of a bicycle and includes a flange which is attached to the derailleur mechanism itself to prevent rotation of the mechanism relative to the bicycle frame. The derailleur guard includes a reinforcing insert member which is also mounted on the rear axle and spaced between the guard and the rear dropout of the bicycle frame.
A disadvantage with this type of guard is that it is attached directly to the rear axle of the bicycle and the rear derailleur so that removal of the derailleur requires the removal of the derailleur guard first. Furthermore, the force of blows delivered to the derailleur guard are transmitted to the derailleur since the guard is attached to the derailleur.
Similarly, Juy U.S. Pat. No. 3,910,136 discloses a rear derailleur guard which comprises a plate shaped to be attached to the idler wheels of the rear derailleur mechanism. While this plate does afford some protection of the idler wheels, a large portion of the derailleur is exposed and, again, the plate is attached directly to the derailleur so that the force of blows sustained by the guard are transmitted directly to the derailleur. Accordingly, there is a need for a derailleur guard for a rear derailleur of a bicycle which does not transmit blows directly to the rear derailleur of the bicycle and, further, does not complicate the procedure for removing the rear derailleur and rear wheel from the bicycle frame.